Procedure for OGTT: The OGTT test will consist of a 75 g of glucose ingestion followed by blood sampling period, with samples collected every 30 min for 240 min. Urine samples will be collected at the end of the infusion and at the end of the OGTT. Blood pressure will be recorded via an automated sphygmomanometer following each blood sample. Oxygen uptake and respiratory exchange rate will be assessed hourly via indirect calorimetry, for a total of seven times per trial. During blood sampling, thirst perception and mouth dryness will be also assessed via visual analog scales.